Dear Ann86,
No surprise to me about your complaints (and ignoral of these) by M&S. VERY many years ago they were reliable and well-run. Size-labels for
off-the-shelf clothing could be relied upon without fitting-check, and covered virtually all sizes. Even though you know what your size(s) is/are, now you have to check in the fitting-rooms (too few of those, as everyone has to check if they REALLY fit, hence long queues). As regards pay-desk the staff, they are less useful than those in the local supermarket. They don't even say "thank you" when you part with your hard-earned cash which pays their wages.
M&S are still trading on Mrs Thatcher's free advertising of them as a great and efficient business (you're too young to know about that).
"Their" products (not made in Britain) are overpriced for the mugs who shop there and their staff down to the absolute minimum, indeed less than that! You EVEN have to stand in a long queue in order to pay, i.e. GIVE THEM YOUR MONEY!
Ann86,your quote about the story you were told about "long length sold out first" was either a lie or bad-business management - if the product clears the racks first, why not increase the available stock and profit? Sounds like the type of shop where you ask for something specific and they say"there's no call for it".
The best retaliation against any lousy don't-care supplier is not to complain but, rather, never go back to them.
Love and happy shopping xxx